The documentation is not very clear ...
By default &whereSearch=`content,tv`.
TV, Jot and Maxigallery are called "joined" tables because they are linked to a "main" table : "site_content".
But you could also define your own main custom table and joined tables.
In any case you need to specify, in first position, a main table and then joined tables. So to search in Jot comments, use
&whereSearch=`content,jot`
If you want search also in tv use &whereSearch=`content,jot,tv`
The documentation needs to be updated and improved. Sorry for the inconvenience.
Look at
http://www.modx.wangba.fr/index.php?id=178 and try with "poupées" as search term. You get a document with some photos. Open the photo "Poupées Russes" and you get a comment regarding the photo. This comment has been found in the search.
"poupées" means "dolls". (beautifull girl) And the comment "poupées Russes" comes from the name of a french Movies, which happens in St Petersburg with beautifull women